Many types of modern electronic devices may incorporate multiple voltage domains. For example, a modern microprocessor chip may include core logic that operates in one voltage domain while interacting with input/output (I/O) circuitry operating in another.
During the initial power up sequencing the different voltage domains may reach a nominal power level at different times. If logic in a first voltage domain is required to function only when the voltages of both domains are at their nominal levels, the logic in the first voltage domain may need an indication that the signal(s) outputted by the second domain logic is(are) valid. Prior art methods have attempted to accomplish this by sending a signal through a level shifter from the second voltage domain to the first voltage domain. Unfortunately, the level shifter output may be an undefined signal if the voltage in the second voltage domain has not reached the nominal voltage level. The propagation of this undefined signal into the first voltage domain could falsely indicate that the signal(s) outputted from the second voltage domain is(are) valid.